High density polyethylene (HDPE) pipe is increasingly being used in fluid carrying lines such as for water and sewer service. HDPE is replacing more conventional pipe materials such as steel, cast iron and asbestos cement because of its lower cost, lighter weight and ease of installation. Because of the lower strength of HDPE pipe, connections between HDPE pipe sections must be reinforced to prevent damage to and leakage from the pipe.
One approach to reinforcing the connection between HDPE pipe sections is shown in the partially cutaway perspective view of FIG. 1. In FIG. 1, a flanged coupling adapter 10 connects a first pipe section 12 to a second, adjacent pipe section 29. The flanged coupling adapter 10 includes first and second end rings 14 and 20. The first end ring 14 includes a generally circular aperture through which the first pipe section 12 is inserted, while the second end ring 20 includes a second generally circular aperture 20a through which the second pipe section 29 is inserted in the direction of arrow 31. A first gasket (not shown for simplicity) is disposed between and engages the first pipe section 12 and the first end ring 14. Similarly, a second gasket 28 is disposed on the inner aperture 20a of the second end ring 20 and engages the second pipe section 29. Flanged coupling adapter 10 further includes four connecting bolts 18a, 18b, 18c and 18d inserted through respective pairs of aligned apertures within the first and second end rings 14, 20. A nut is disposed on the end of each of the four connecting bolts 18a, 18b, 18c and 18d for securely coupling the first and second end rings 14, 20. In FIG. 1, nuts 22a, 22c and 22d are shown threadably engaging bolts 18a, 18c and 18d, respectively. A cylindrical center ring 16 is disposed within and extends between the first and second end rings 14, 20. Center ring 16 is further concentrically disposed about adjacent ends of the first pipe section 12 and the second pipe section 29 and encompasses the juncture between these two pipe sections. For illustrative purposes, center ring 16 is shown partially cutaway as having an aperture 16a therein. In actual use, center ring 16 forms a full cylinder about adjacent ends of the two joined pipe sections. Tapered portions of the flanged coupling adapter 10 form a tight-fitting seal about the two joined pipe sections when the nut and bolt combinations connecting the first and second end rings 14, 20 are securely tightened.
The prior art pipe coupling arrangement shown in FIG. 1 further includes a pipe stiffener 24 inserted within the adjacent open ends of each of the first and second joined pipe sections. An exploded perspective view of the pipe stiffener 24 inserted within the open end of the first pipe section 12 is shown in FIG. 2. A similar pipe stiffener is inserted in the adjacent open end of the second pipe section 29, although this is not shown in the figures for simplicity. Stiffener 24 is generally cylindrical in shape and includes opposed first and second open ends, with the first open end shown in FIG. 2 as element 24a. Extending the length of the stiffener 24 is a tapered slot defined by first and second opposed, inner tapered edges 24b and 24c. An end lip 24d is disposed about the first open end 24a of the pipe stiffener 24 and limits the extent of insertion of the pipe stiffener in the open end of a pipe and affords a high strength portion of the stiffener for pounding the stiffener into an open pipe end such as with a hammer.
Pipe stiffener 24 further includes a dual-tapered wedge 26 having first and second opposed, tapered edges 26a and 26b. Attached to the first tapered edge 26a are a first set of spaced connecting tabs, or clips, 30. Similarly, attached to the second tapered edge 26b are a second set of spaced connecting tabs 32. Each of the aforementioned connecting tabs includes a respective slot which is adapted to receive one of the inner tapered edges of the pipe stiffener 24. Thus, a slot within each of the first set of connecting tabs 30 is adapted to securely engage the first inner tapered edge 24b of the pipe stiffener 24, while a slot in each of the second set of connecting tabs 32 is adapted to securely engage the second inner tapered edge 24c of the pipe stiffener. With the pipe stiffener 24 inserted within the open end of the first pipe section 12, dual-tapered wedge 26 is inserted within the tapered slot in the pipe stiffener such that each connecting tab engages an inner tapered edge of the pipe stiffener. The dual-tapered wedge 26 is then firmly positioned within the pipe stiffener 24 by striking the wider end of the pipe stiffener having end lip 24d with a rubber hammer so that it extends the length of the pipe stiffener within the tapered slot therein. The lead-in end of the tapered slot within the pipe stiffener 24 includes first and second cut-out portions 34a and 34b respectively disposed on tapered edges 24c and 24b. These cut-out portions 34a,34b allow wedge 26 to be inserted in the lengthwise slot in the pipe stiffener 24, but weaken the strength of the stiffener arrangement.
While the pipe connecting arrangement of FIGS. 1 and 2 operates reasonably well, it has several shortcomings. For example, the dual-tapered wedge 26 requires a tapered roller for its fabrication which increases the cost of the pipe stiffener. In addition, each of the first and second sets of connecting tabs 30, 32 must be precisely positioned on opposed tapered edges of the wedge 26 to securely engage the opposed tapered inner edges of the pipe stiffener 24. This also increases the cost and complexity of manufacturing the pipe stiffener. In addition, connecting tabs 30, 32 extend into the flow path of the medium carried by the coupled pipes and disturb the flow characteristics of the medium. Finally, because proper positioning of the dual tapered wedge 26 within the tapered slot in the pipe stiffener 24 requires precise positioning of the connecting tabs on the wedge, inserting the wedge so that its wider end is flush with the end lip 24d of the pipe stiffener is frequently not feasible, resulting in the wider end of the wedge extending beyond or outside of the end lip of the pipe stiffener. This results in a gap between the coupled pipe ends and makes it more difficult to seal the pipe connection in a leak-proof manner.
The present invention addresses the aforementioned limitations of the prior art by providing a pipe stiffener for securely coupling pipe sections in a sealed manner which is easily fabricated and installed and which does not disturb the flow characteristics of a medium carried by the pipes.